USEUROPEAFRICAASIA 中文雙語Fran?ais
    China
    Home / China / World

    Alaska studies glacier's surges

    By Kirk Johnson | The New York Times | Updated: 2013-08-04 07:19

     Alaska studies glacier's surges

    "Glacier leap," or melting that leads to a sudden release of water, is occurring at Mendenhall Glacier in Juneau. Photograph by Matthew Ryan Williams for The New York Times

    JUNEAU, Alaska - The idea that glaciers change at a glacial speed is increasingly false. They are melting and retreating rapidly all over the world. But the unpredictable flood surges at the Mendenhall Glacier, about 20 kilometers from downtown Juneau, Alaska's capital, are especially worrisome as global temperatures and climate variability increase.

    Starting in July 2011, and each year since, sudden torrents of water shooting out from beneath the glacier have become a new facet of Juneau's brief, shimmering high summer season. In that first, and so far biggest, measured flood burst, an estimated 37 billion liters gushed out in three days, threatening homes and property along the Mendenhall River that winds through part of the city. There have been at least two smaller bursts this year.

    "That first one caught us by surprise," said Tom Mattice, the emergency programs manager and avalanche forecaster for Juneau.

    That the Mendenhall Glacier is thinning, and has been for decades, is only part of the explanation. Water from snowmelt, rain and thawing is are also combining in new ways, researchers said - first pooling in an ice-covered depression near the glacier called Suicide Basin, then finding a way to flow downhill.

    What prompts a surge - and the urgent search for a way to anticipate and prepare by scientists and safety officials like Mr. Mattice - is pressure. As water builds up in the basin and seeks an outlet, it can lift portions of the glacier ever so slightly, and in that lift, the water finds a release. Under the vast pressure of the ice bearing down upon it, the water explodes out into the depths of Mendenhall Lake and from there into the river.

    Glaciologists even have a name for the process, which is happening in many places all over the world as climates change: jokulhlaup, an Icelandic word usually translated as "glacier leap."

    "We don't have a sense yet how much of a threat this poses, or how much water you could store up there," said Jason Amundson, an assistant professor of geophysics at the University of Alaska Southeast, in Juneau.

    What elevates the concern is the proximity of people. Glaciers may be leaping in many places, but it happens mostly in isolation. The roughly 20-kilometer-long Mendenhall, by contrast, is one of the most visited glaciers in the world, and an urban one. About 400,000 tourists a year, 80 percent of them from the cruise ships that stop at the Port of Juneau, are drawn to the glacier.

    "We're a drive-up glacier," said Nikki Hinds of the Mendenhall Glacier Visitor Center, which is operated by the United States Forest Service. "In how many places can you have that?"

    This summer, glacier-monitoring intensified. A pressure transducer to gauge water buildup was installed in a deep crack on the edge of the basin, with a satellite link sending back real-time data about the glacier's hidden waterworks. A time-lapse camera was also positioned at the main pooling site for the first time to track bulges in the ice that could suggest dammed-up water.

    Like glaciers the world over, the Mendenhall has thinned and retreated more than a hundred meters since visitors first started coming here in the late 1800s. Long-term climate models suggest a warmer, wetter pattern in this part of Alaska, which could have its own strange ripple of consequences for the Mendenhall and the people who love it, study it and live by it.

    Jamie Pierce, a mountaineer and researcher at the university, was out on the Mendenhall ice on a recent afternoon, checking the instruments. After rappelling about 15 meters to the transducer, he found it completely dry, suggesting that the water was finding another channel or another damming point, other than the one suspected of causing the trouble.

    Mr. Pierce said, "The biggest thing we don't know is what's blocking what."

    The New York Times

    Editor's picks
    Copyright 1995 - . All rights reserved. The content (including but not limited to text, photo, multimedia information, etc) published in this site belongs to China Daily Information Co (CDIC). Without written authorization from CDIC, such content shall not be republished or used in any form. Note: Browsers with 1024*768 or higher resolution are suggested for this site.
    License for publishing multimedia online 0108263

    Registration Number: 130349
    FOLLOW US
    亚洲av无码一区二区乱子伦as| 亚洲综合中文字幕无线码| 免费无码午夜福利片| 韩日美无码精品无码| 日韩av无码中文无码电影| 精品国产a∨无码一区二区三区 | 无码成A毛片免费| 亚洲一日韩欧美中文字幕欧美日韩在线精品一区二 | 亚洲AV无码专区国产乱码电影| 亚洲中文字幕无码一区二区三区 | 国产成人AV一区二区三区无码| 蜜桃AV无码免费看永久| 天堂√最新版中文在线天堂| 亚洲熟妇少妇任你躁在线观看无码| 99精品一区二区三区无码吞精| 亚洲av永久无码精品国产精品| 日韩精品无码免费专区午夜| 亚洲欧美日韩中文字幕一区二区| 国产精品 中文字幕 亚洲 欧美| 少妇无码太爽了不卡视频在线看 | 亚洲一区二区无码偷拍| 超清纯白嫩大学生无码网站| 久久青青草原亚洲av无码app| 亚洲AV无码乱码国产麻豆穿越 | 亚洲精品无码午夜福利中文字幕| 中文字幕日本精品一区二区三区 | 日韩av无码免费播放| 中文字幕一区二区三区永久 | 色偷偷一区二区无码视频| 亚洲AV永久无码精品| 亚洲成av人片在线观看无码不卡 | 日韩丰满少妇无码内射| 亚洲Av永久无码精品三区在线 | 精品无码日韩一区二区三区不卡| 日韩精品无码一区二区中文字幕 | 人妻丰满熟妇A v无码区不卡| 国产综合无码一区二区三区| 日韩乱码人妻无码中文视频| 亚洲AV中文无码乱人伦在线观看 | 中文字幕你懂的| 性无码专区一色吊丝中文字幕|